1. Field of the Invention
The present invention relates to a recording-material identifying apparatus configured to pick up an image of the surface of a recording material to identify the surface properties thereof, and to an image forming apparatus configured to control image-forming conditions based on the identification result.
2. Description of the Related Art
In a conventional image forming apparatus, a user sets the type (size, etc.,) of a recording material through a computer, serving as an external apparatus, an operation panel provided on the body of the image forming apparatus, or the like. Transfer conditions (transfer voltage and conveyance speed of the recording material during transfer) at a transfer unit, fixing conditions (fixing temperature and conveyance speed of the recording materials during fixing), etc., are controlled based on the user's setting.
To spare users from such an inconvenience, namely, setting the type of the recording material through a computer or an operation panel, there has been provided an image forming apparatus having a sensor for identifying the type of a recording material to automatically identify the type of the recording material. Such an image forming apparatus having the sensor automatically identifies the type of a recording material and is controlled such that the transfer conditions, the fixing conditions, etc., are set based on the identification result.
More specifically, as disclosed in Japanese Patent Laid-Open No. 2002-182518, an image of the surface of a recording material is picked up using a complementary metal-oxide-semiconductor (CMOS), and the surface smoothness is detected from the picked-up image to identify the type of the recording material. Then, the image forming conditions are determined based on the identification result.
In such an apparatus that picks up an image of the surface of the recording material, a precise image of the surface of the recording material is picked up by making the distance between the recording material and the sensor constant. For example, Japanese Patent Laid-Open No. 2002-111964 proposes a configuration in which, while a recording material is pressed by a pressing member, a surface image of a part not pressed by the pressing member is read.
In some cases, the identification accuracy can be improved by reading a surface image of a part not pressed by the pressing member, as in the case of Japanese Patent Laid-Open No. 2002-111964 described in the related art section. However, depending on the type of the recording material, the identification accuracy can be improved by reading a surface image of a part pressed by the pressing member. Therefore, with a sensor having the structure disclosed in Japanese Patent Laid-Open No. 2002-111964, the identification accuracy is decreased in certain types of the recording material. Although it is possible to pick up a surface image of a part not pressed by the pressing member and a surface image of a part pressed by the pressing member using separate sensors, such a configuration leads to an increase in cost because it requires two sensors.